The invention relates to an apparatus for efficiently depositing thin film coatings on a substrate. More specifically, the invention relates to an apparatus which permits the deposition of certain thin films at commercially viable deposition rates and having desired properties, which heretofore have not been possible with conventional deposition apparatus.
Two categories of thin films have been known for some years. They are distinguishable in many ways, but for purposes of this application, the primary areas of distinction are (1) the method of deposition, i.e. on-line versus offline and (2) the types of films generally produced by such methods, respectively, hard coat (or pyrolytic) versus soft-coat.
On-line coatings are preferably produced by deposition of one or more thin film layers on, for example, a glass substrate during the glass manufacturing process, typically a continuous float glass manufacturing process. As a consequence of the characteristics of the float glass manufacturing process the thin film deposition process must take place at relatively high temperatures, with very short chemical reaction times, but at high deposition rates, in order to be commercially viable.
In a successful on-line coating operation, the thin films produced are relatively mechanically and chemically durable compared to most soft-coat films.
Off-line film deposition, typically, involves one of several known types of sputter coating processes, in which glass panels are placed in one or more coating chambers where the glass panel is exposed to an atmosphere created by the physical or chemical reaction of a “target” material so that it is deposited on a surface of the glass panel. As the sputtering process is not controlled by the speed of the glass manufacturing process, it may be possible to deposit more complex film stacks by sputtering processes, which film stacks may, in some instances have properties superior to those of pyrolytic thin films, but such sputtered films are also likely to be significantly more expensive to produce.
Apparatus for on-line coating are known in the patent literature, for example:
U.S. Pat. No. 4,446,815 describes a nozzle having three converging tuyeres which project the reagents in the gaseous phase onto a substrate. Deflector members are adapted to channel the gases between themselves and the substrate, extending on either side of the nozzle. The surface of a first deflector member extends in the opposite direction to the direction of movement of the substrate with respect to the nozzle, is parallel to the substrate, and forms an acute angle with the extended external wall of the third tuyere, so as to be transversely offset in the direction of substrate movement with respect to the axial median plane of the first tuyere. By contrast, the surface of the second deflector member forms a blunt edge with the corresponding longitudinal wall of the second tuyere. The opening of the nozzle between the edges of the first and second deflector members is therefore effectively bent, and the gases emerging therefrom are regularly deflected in the direction of movement of the substrate.
U.S. Pat. No. 4,834,020 describes a conveyorized atmospheric chemical vapor deposition apparatus having a heated muffle furnace and a conveyor belt for conveying objects to be coated through the furnace. At least one chemical vapor deposition zone is provided in the muffle furnace. An injector assembly is also provided for uniformly injecting first and second reactant gases in the deposition zone across the width of the conveyor belt and against the surfaces of the objects to be coated. The gases exit from slots connected to distribution plenums. Polished cooled surfaces are used on the injector assembly for the purpose of minimizing deposition of chemicals thereon.
U.S. Pat. No. 5,041,150 describes a process for coating a moving ribbon of hot glass by chemical vapor deposition by establishing a first flow of a first reactant gas along the hot glass surface substantially parallel to the direction of movement of the glass, and establishing a second flow of a second reactant gas as a turbulent flow at an angle to the glass surface, thus introducing said second flow into said first flow at said angle, while avoiding upstream flow of the second reactant gas in the first flow, and directing the combined first and second gas flows along the surface of the hot glass as a turbulent flow.
U.S. Pat. No. 5,122,391 describes an atmospheric pressure chemical vapor deposition system for doping indium oxide films with both tin and fluorine said to produce dual electron donors in a non-batch process. The deposition system has a conveyor belt and drive system for continuous processing through one or more reaction chambers separated by nitrogen purge curtains. A substrate passing through the system enters a muffle furnace heated by several heaters and the reaction chambers are supplied by a source chemical delivery system comprising an oxidizer source, a fluorine chemical source, a nitrogen source, rotometers for the above sources, a mass flow controller, a tin chemical bubbler, heated lines, an indium chemical bubbler, a pair of water baths with heaters, and associated valving.
U.S. Pat. No. 5,136,975 describes an injector of a type said to be used in atmospheric pressure chemical vapor deposition equipment. The injector includes a number of plates with a number of linear hole arrays. The plates are layered in order to produce a number of what are called cascaded hole arrays. The layered plates together are said to define a hole matrix. A chute is positioned beneath the hole matrix. On both sides of the chute is a cooling plate. The chute includes a passage and the regions between the cooling plates and the chute form ducts. The top of the hole matrix receives a number of gaseous chemicals and discretely conveys them to the top of the individual cascade hole arrays. The gaseous chemicals are then forced through the cascaded hole arrays which induces the gases to flow in an increasingly uniform manner. The gaseous chemicals are then individually fed to the passage and ducts which convey them to a region above the surface where the chemicals are exposed to one another, react and form a layer on a substrate surface.
U.S. Pat. No. 5,704,982 describes a nozzle for distributing at least one current of precursor gases onto a surface of a moving glass substrate by pyrolysis/decomposition reaction, includes a nozzle body, a principal gas feed system for feeding at least one current of precursor gases into the nozzle of the body, and an auxiliary gas feed system independent of the principal gas feed system, for feeding at least one of the precursor gases to the nozzle body in the proximity of the principal gas of the nozzle body for locally modifying the chemical composition of the principal gas. The auxiliary gas flow into the nozzle body is controlled at a flow rate which is variable in time.
U.S. Pat. No. 6,022,414 describes a single body injector for delivering gases to a surface. The injector is comprised of an elongated member with end surfaces and at least one gas delivery surface extending along the length of the member and which includes a number of elongated passages formed therein. Also formed within the member are a number of thin distribution channels which extend between the elongated passages and the gas delivery surface. Gases are conveyed to the elongated passages, through the distribution channels to the gas delivery surface where they are directed to a desired region where they mix, react and form a thin film on the substrate positioned beneath the injector. The gas delivery surface is comprised of rounded side regions and a center recessed region of the gas delivery surface.
U.S. Pat. No. 6,206,973 describes a chemical vapor deposition system including a heated muffle, a chamber having an injector assembly for introducing vaporized chemical reactants, and a belt for moving the substrate through the muffle and chamber. The belt has an oxidation-resistant coating to reduce formation of deposits thereon, particularly deposits of chromium oxides.
U.S. Pat. No. 6,521,048 describes a chemical vapor deposition apparatus comprising a deposition chamber and a main chamber. The deposition chamber comprises at least one single injector and one or more exhaust channels. The main chamber supports the deposition chamber and includes at least one gas inlet to inject at least one gas into the main chamber. The gases are removed through the exhaust channels, thereby creating an inwardly flowing purge which acts to isolate the deposition chamber. At least one so-called semi-seal is formed between the deposition chamber and the substrate so as to confine the reactive chemicals within each deposition region.
U.S. Pat. No. 6,890,386 describes an injector and exhaust assembly for delivering gas to a substrate comprising at least two injectors positioned adjacent each other and spaced apart to form at least one exhaust channel therebetween, and a mounting plate for securing the at least two injectors, wherein each of the at least two injectors are individually mounted to or removed from the mounting plate, the mounting plate being provided with at least one exhaust slot in fluid communication with the at least one exhaust channel. An exhaust assembly is coupled to the mounting plate to remove exhaust gases from the injectors.